1. Field of the Invention
The present invention relates to a display device and a display method.
2. Description of the Related Art
A plasma display (gas discharge display device) is a large scale flat panel display, and is becoming increasingly popular also as wall-mount home television set. For achieving more popularity there are demanded brightness, quality of display and price not falling short of the ones being achievable using the CRT.
For the plasma display, there occurs a problem of streaking as described below. When the number of pixels to be lighted simultaneously is large within a line, voltage drop due to the resistance becomes large, and the emission of light of the pixels to be lighted is made dark. On the other hand, when the number of pixels to be lighted simultaneously within a line is small, the emission of light of the pixels to be lighted is made relatively bright. In this way different lines lead to different brightness even in the event of carrying out the display at the same gradation level or gray value. As the difference in brightness becomes larger, the percentage representation of the streaking is made larger, which is not preferable.
In connection with the AC type color plasma display, a further increase in the light emission efficiency and decrease in streaking are required, and driving methods of sustaining discharge are being developed. The sustaining pulse such as in the 2-step discharge (See, for example, Patent document 1, below.) and the pop discharge (See, for example, Patent document 2, below.) is such that the discharge peak intensity decreases; the light emission efficiency increases; and the streaking decreases caused by the difference in voltage drop between electrodes, but there is a problem of decrease in the peak luminance.
For example, in the 2-step discharge the sustaining pulses rise in two steps, wherein in the first step voltage of the sustaining pulse a weak discharge is generated and in the second step of the sustaining pulse a sustaining discharge is generated successively. By using the 2-step discharge waveform, since a discharge current peak is small, a voltage drop in the wiring line is small, consequently resulting in a reduction in streaking. It is also distinctive feature that small discharge intensity and reduction in ultraviolet light emission and saturation in the fluorescent material or the like lead to the light emission efficiency higher by 10% or more. Nevertheless, due to the small peak discharge current, emission intensity by a single shot is lower, and the pulse width becomes broader due to the 2-step waveform, with the result that it is impossible to increase the number of the sustaining pulses, and peak luminance decreases by 20%.
In order to realize both of high emission efficiency/decrease in streaking and high luminance, it might be conceivable to change the sorts of the sustaining pulse depending upon a state of display, but a switching shock would pose a problem since luminance and chromaticity would vary depending on sorts of the pulses. To overcome the problem of this switching shock, it might also be conceivable to allow the sustaining pulses in a sub-frame to be comprised of two sorts of sustaining pulse and to change gradually the proportion of these two sorts of the sustaining pulse. But since the state of discharge/wall charge varies depending on the sort of the sustaining pulse, the display operation becomes unstable, and further control thereof is also made difficult.
[Patent document 1] Japanese Patent Application Laid-open No. 2000-148083
[Patent document 2] Japanese Patent Application Laid-open No. 2003-29700